DM-RS of Pi/2-BPSK Signals

ABSTRACT

According to certain embodiments, a method performed by a wireless device for transmitting a demodulation reference signal (DMRS) includes obtaining a first spreading function for spreading a first pi/2-BPSK sequence to occupy a first subset of a plurality of subcarriers in a frequency domain. A first DMRS is generated by applying the first spreading function to the first pi/2-BPSK sequence. The first DMRS is transmitted to a network node.

TECHNICAL FIELD

The present disclosure relates, in general, to wireless communications and, more particularly, systems and methods for demodulation reference signal of pi/2-binary phase shift keying (pi/2-BPSK) signals.

BACKGROUND

Third Generation Partnership Project (3GPP) specifications may include pi/2 binary phase shift keying (BPSK) modulation for physical uplink shared channel (PUSCH) and for physical uplink control channel (PUCCH). In pi/2 BPSK modulation, the modulation symbols are taken out of a 1-dimensional signaling alphabet (BPSK), but the signaling alphabet is rotated by pi/2 (i.e., 90 degrees) between symbols. For example, for even time instances (0, 2, 4, . . . ) real-values BPSK (±1) and for odd time instances (1, 3, 5, . . . ) imaginary-valued BPSK (±j) is used (it is also possible to use (−1−j, 1+j) and (−1+j, 1−j) or similar as long as consecutive signaling alphabets are rotated by pi/2).

FIG. 1 illustrates an example of alternating real and imaginary valued BPSK signaling alphabets. Specifically, FIG. 1 illustrates a bit transition 0→1 (or reverse) does not lead to a zero crossing, but at most to a pi/2 phase shift of the modulation symbols. Avoiding zero crossing prevents and/or reduces ringing of the waveform, which reduces peak to average power ratio (PAPR) and cubic metric (CM).

Pi/2 BPSK is often used together with pulse shaping, see FIG. 2. The pulse shaping function has low pass characteristic and smoothens the waveform further reducing PAPR/CM. It is expected that in NR most pi/2 BPSK signaling schemes will use pulse shaping to further improve PAPR/CM.

If the pulse shaping block is cyclic (i.e., performs cyclic convolution with period M instead of linear convolution) and the pulse shaping filter has at most M taps (where M is the discrete Fourier transform (DFT) size of the DFT precoder), the input to the DFT-spreading block is periodic with periodicity M. The pulse shaper takes M input symbols and cyclically pulse shapes the blocks of M symbols. A cyclic pulse shaper, which is time-domain-based, can be exchanged with a frequency-domain spectrum shaper (FDSS) which multiplies the frequency-domain samples with the DFT of length M of the time-domain pulse shape.

For DFTS-OFDM-based PUSCH, demodulation reference signal (DM-RS) symbols and data-carrying symbols are multiplexed using time division multiplexing (TDM) structure to maintain low PAPR/CM. For pi/2 BPSK, a similar signaling structure to FIG. 2 is used for data-carrying symbols. For PUSCH data, the data bits are encoded (e.g., low-density parity code (LDPC), Turbo, Polar, for new radio (NR): preferably LDPC), optionally scrambled, and mapped to a modulation symbol, in case of pi/2 BPSK to pi/2 BPSK symbols.

The pulse shaping function used in the pulse shaper is proprietary and not specified in the standard. The pulse shape may fulfill some flatness criteria, but its exact shape is left to a user equipment (UE) vendor. Therefore, the gNB does not know the pulse shape. To enable demodulation, a DM-RS symbol must apply the same pulse shaping as data-carrying symbols. FIG. 2 applies, therefore, to both DM-RS and data-carrying symbols.

Depending on the scheduling bandwidth, DM-RS sequences for DFTS-OFDM PUSCH based on quadrature phase-shift keying (QPSK) and quadrature amplitude modulation (QAM) are either based on Zadoff-Chu sequences (cyclic extended or truncated to obtain the required length) or based on computer-optimized QPSK sequences. DM-RS sequences for pi/2 BPSK are not specified.

3GPP specifications may also support pi/2 BPSK for long PUCCH formats for more than 2 bits. Long PUCCH for more than 2 bits has a similar structure per OFDM symbol as PUSCH, which was illustrated in FIG. 2. For uplink control information (UCI)-carrying symbols, the encoded UCI may be encoded using Turbo, LDPC, Polar, or Reed Muller. Preferred encoding may be LDPC or Reed Muller, in particular embodiments. Encoded bits can be scrambled and then mapped to QPSK or pi/2 BPSK symbols. Also for PUCCH, DM-RS symbols should apply the same pulse shaping as data symbols. For PUCCH, the same DM-RS sequences may be used as for PUSCH.

Long PUCCH for more than 2 bits comes in a variant without user-multiplexing on the same physical resource block (PRB) and in a variant that enables multiplexing of two and four users on the same PRB.

There currently exist certain challenge(s). For example, all existing DM-RS designs for both PUSCH and long PUCCH are either based on Zadoff-Chu sequences or computer-optimized QPSK sequences. Zadoff-Chu sequences (and also computer optimized QPSK sequences) have good PAPR/CM properties without spectrum shaping and enable creation of orthogonal DM-RS via cyclic shifting of the base Zadoff-Chu (computer optimized) sequence. However, with pulse shaping, the average PAPR/CM across multiple root sequences of Zadoff-Chu sequences degrades. Compared with DM-RS based on pulse-shaped pi/2 BPSK sequences, pulse-shaped Zadoff-Chu sequences might have 1-1.5 dB higher CM.

From a PAPR/CM perspective, it is advantages to use pulse shaped pi/2 BPSK sequences as DM-RS sequences. A drawback is that, without special design, pulse-shaped pi/2 BPSK sequences occupy all M subcarriers after the DFT-spreading operation in FIG. 2. For PUSCH, pi/2 BPSK DFTS-OFDM PUSCH cannot be MU-MIMO multiplexed with regular DFTS-OFDM or OFDM-based PUSCH because pulse-shaped pi/2 BPSK DM-RS and other PUSCH DM-RS are not orthogonal.

SUMMARY

To address the foregoing problems with existing solutions, disclosed is systems and methods for transmitting and receiving demodulation reference signal (DMRS).

According to certain embodiments, a method performed by a wireless device for transmitting a DMRS includes obtaining a first spreading function for spreading a first pi/2-BPSK sequence to occupy a first subset of a plurality of subcarriers in a frequency domain. A first DMRS is generated by applying the first spreading function to the first pi/2-BPSK sequence. The first DMRS is transmitted to a network node.

According to certain embodiments, a wireless device is provided for transmitting a DMRS. The wireless device includes memory storing instructions and processing circuitry operable to execute the instructions to cause the wireless device to obtain a first spreading function for spreading a first pi/2-BPSK sequence to occupy a first subset of a plurality of subcarriers in a frequency domain. The processing circuitry generates a first DMRS by applying the first spreading function to the first pi/2-BPSK sequence and transmits the first DMRS to a network node.

According to certain embodiments, a method by a network node is provided for receiving a DMRS. The method includes receiving a first DMRS generated using a first spreading function applied to a first pi/2-BPSK sequence such that the first DMRS occupies a first frequency comb that is a first subset of a plurality of subcarriers in the frequency domain. The method also includes receiving a second DMRS occupying a second frequency comb that includes a second subset of the plurality of subcarriers in the frequency domain.

According to certain embodiments, a network node is provided for receiving a DMRS. The network node includes memory storing instructions and processing circuitry operable to execute the instructions to cause the network node to receive a first DMRS generated using a first spreading function applied to a first pi/2-BPSK sequence such that the first DMRS occupies a first frequency comb that is a first subset of a plurality of subcarriers in the frequency domain. The processing circuitry also receives a second DMRS occupying a second frequency comb that includes a second subset of the plurality of subcarriers in the frequency domain.

Certain embodiments may provide one or more of the following technical advantage(s). For example, certain embodiments may generate multiple orthogonal DM-RS sequences based on pulse shaped pi/BPSK. As a result, certain embodiments may enable PUSCH MU-MIMO or PUCCH multiplexing of multiple users. Because the DM-RS are based on pulse shaped pi/2 BPSK sequences, the PAPR/CM may be low for some embodiments.

Other advantages may be readily apparent to one having skill in the art. Certain embodiments may have none, some, or all of the recited advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosed embodiments and their features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates an example of alternating real and imaginary valued BPSK signaling alphabets;

FIG. 2 illustrates the basic DM-RS structure with the input sequence to the pulse shaper comprising a pi/2 BPSK sequence, according to certain embodiments;

FIG. 3 illustrates that the first sample or first few samples of a cyclic prefix are either set to zero or are a function of the last or last few samples of the previous DFTS-OFDM symbol, according to certain embodiments;

FIG. 4 illustrates an example network, according to certain embodiments;

FIG. 5 illustrate an example network node, according to certain embodiments;

FIG. 6 illustrates an example wireless device, according to certain embodiments;

FIG. 7 illustrates an example user equipment (UE), according to certain embodiments;

FIG. 8 illustrate an example virtualization environment in which functions implemented by some embodiments may be virtualized, according to certain embodiments;

FIG. 9 illustrates an example telecommunication network connected via an intermediate network to a host computer, according to certain embodiments;

FIG. 10 illustrates an example host computer communicating via a base station with a user equipment over a partially wireless connection, according to certain embodiments;

FIG. 11 illustrates an example method implemented in a communication system, in accordance with one embodiment;

FIG. 12 illustrates another example method implemented in a communication system, in accordance with one embodiment;

FIG. 13 illustrates another example method implemented in a communication system, in accordance with one embodiment;

FIG. 14 illustrates a method implemented in a communication system, in accordance with one embodiment;

FIG. 15 illustrates an example method by a wireless device, according to certain embodiments;

FIG. 16 illustrates an example virtual apparatus, according to certain embodiments;

FIG. 17 illustrates another example method by a wireless device, according to certain embodiments;

FIG. 18 illustrates another example virtual apparatus, according to certain embodiments;

FIG. 19 illustrates an example method by a network node, according to certain embodiments;

FIG. 20 illustrates another example virtual apparatus, according to certain embodiments;

FIG. 21 illustrates another example method by a network node, according to certain embodiments; and

FIG. 22 illustrates another example virtual apparatus, according to certain embodiments.

DETAILED DESCRIPTION

Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.

There are, proposed herein, various embodiments which address one or more of the issues discussed above. For example, certain embodiments described herein to map DM-RS for pi/2 BPSK on a comb in frequency-domain. If DM-RS for (regular) DFTS-OFDM or OFDM-based PUSCH occupy another comb, orthogonal DM-RS can be created. Also, for long PUCCH with user multiplexing, multiple (two or more) orthogonal DM-RS may enable multiplexing of multiple users onto the same PRB.

In general, certain embodiments include a DM-RS design for pi/2 BPSK (with pulse shaping, also referred to as frequency-domain spectrum shaping) to obtain good PAPR/CM. The pi/2 BPSK sequences are designed to occupy a comb in frequency-domain, even if pulse shaping is applied. Multiple DM-RS sequences occupying different frequency-domain combs can be generated, enabling PUSCH MU-MIMO or PUCCH multiplexing of multiple users.

A pi/2 BPSK sequence is block-spread with spreading sequences that maps the different DM-RS sequences to different combs. Due to the spreading, some resulting sequences may have zero crossings. The sequences can optionally be removed from the set of DM-RS. Furthermore, the pulse shaper is constructed to perform a cyclic convolution.

Some of the embodiments contemplated herein will now be described more fully with reference to FIGS. 2-22. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

FIG. 2 illustrates the basic DM-RS structure with the input sequence to the pulse shaper comprising a pi/2 BPSK sequence, according to certain embodiments. However, in particular embodiments, restrictions are applied to the sequence to ensure that the sequence only occupies a comb in frequency-domain. Multiplexing DM-RS to occupy different combs enables multiple orthogonal DM-RS. Orthogonality may be maintained with a different class (but still comb based) of DM-RS as long as different combs are occupied.

In a particular embodiment, the input pi/2 BPSK sequence is constructed based on a pi/2 BPSK sequence of length M/L with M the size of the DFT precoder and L the desired frequency-domain comb spacing. L is thus the number of orthogonal DM-RS that can be obtained via frequency-domain multiplexing. Typical examples of L would be 2 or 4. The DFT precoder M determines the bandwidth of the DM-RS. For example, DM-RS for one PRB may use an M value of 12. For two PRB, M may be 24, and so on. L is equal to 2 for two orthogonal DM-RS.

For example, a pi/2 BPSK sequence of length M/L may be constructed such as, for example, x₀=[re im re im . . . ] where re and im are BPSK modulation symbols taken from pi/2 rotated BPSK signaling alphabets. In a particular embodiment, for example, re could be taken from ±1 and im could be taken from ±j. However, any other pi/2 shifted signaling alphabets may be used. As used herein, re and im are placeholders for the modulation symbols taken from the two pi/2 rotated signaling alphabets. An example of x₀ of length 6 could be x₀=[re₀, im₀, re₁, im₁, re₂, im₂] with re_(i) and im_(i) taken from the two pi/2 rotated signaling alphabets, respectively. For M=12, first and second DM-RS can be generated as follows:

y ₀=[x ₀ , x ₀]=[re ₀ , im ₀ , re ₁ , im ₁ , re ₂ , im ₂ , re ₀ , im ₀ , re ₁ , im ₁ , re ₂ , im ₂]

y ₁=[x ₀ , −x ₀]=[re ₀ , im ₀ , re ₁ , im ₁, re₂ , im ₂ , −re ₀ , −im ₀ , −re ₁ , −im ₁ , −re ₂ , −im ₂]

For M values other than 12, another sequence x₀ may be used. For example, for M=24 an x₀ sequence of length 12 may be used. For L=2, the same block-spreading sequences [1, 1] and [1, −1] would be used (the two block spreading sequences are the rows of a DFT(2) matrix).

Because of block spreading by DFT(2), matrix row (or column), y₀, occupies only even numbered subcarriers and matrix row (or column), y₁, occupies odd subcarriers. Thus, the two sequences are orthogonal. The pi/2 BPSK construction, wherein adjacent symbols are taken from different signaling alphabets, is fulfilled for both DM-RS. Specifically, a re is always followed by an im, and zero crossings are avoided. Because a cyclic prefix is added after the OFDM modulation, it is preferable in some embodiments if the last sample of the DM-RS sequence (im₂ and −im₂ for y₀ and y₁, respectively) use a different signaling alphabet than the first sample of the DM-RS sequences (re₀ for both y₀ and y₁), which is fulfilled for both DM-RS sequences.

In a particular embodiment, instead of a DFT(2) matrix, any matrix derived from it via scaling, conjugate, transpose, and/or row and/or column cyclic shifting may be used.

The embodiments described above (i.e., where y₀ and y₁ occupy different combs) are so far restricted to before the pulse shaping filter. If the pulse shaper implements a cyclic convolution with the pulse shaping filter, which means the pulse shaping filter has M or fewer non-zero (significant) coefficients, the time-domain pulse shaping is equivalent to a frequency-domain multiplication. The comb structure is maintained after a frequency-domain multiplication such that y₀ and y₁ remain orthogonal (mapped to different frequency-domain combs) if the pulse shaped implements a cyclic convolution.

In particular embodiments, L=4 with up to 4 orthogonal DM-RS. A pi/2 BPSK sequence of length M/L is constructed, i.e. x₀=[re im re im . . . ] where re and im are BPSK modulation symbols taken from pi/2 rotated BPSK signaling alphabets. For example, re could be taken from ±1 and im could be taken from ±j. However, any other pi/2 shifted signaling alphabets may be used. As used herein, re and im are placeholders for the modulation symbols taken from the two pi/2 rotated signaling alphabets. An example of x₀ of length 3 could be x₀=[re₀, im₀, re₁] with re_(i) and im_(i) taken from the two pi/2 rotated signaling alphabets, respectively. For M=12, four DM-RS can be constructed by block-spreading a length-3 x₀ sequence with the rows (columns) of a DFT(4) matrix or another matrix derived from it e.g. via scaling, conjugate, transpose, row and/or column cyclic shifting). The obtained DM-RS may be as follows:

y ₀=[x ₀ , x ₀ , x ₀ , x ₀]=[re ₀ , im ₀ , re ₁ , re ₀ , im ₀ , re ₁ , re ₀ , im ₀ , re ₁ , re ₀ , im ₀ , re ₁]

y ₁=[x ₀ , −jx ₀ , −x ₀ , jx ₀]=[re ₀ , im ₀ , re ₁ , −j·re ₀ , −j−im ₀ , −j·re ₁ , −re ₀ , −im ₀ , −re ₁ , j·re ₀ , j·im ₀ , j·re ₁]

y ₂=[x ₀ , −x ₀ , x ₀ , −x ₀]=[re ₀ , im ₀ , re ₁ , −re ₀ , −im ₀ , −re ₁ , re ₀ , im ₀ , re ₁ , −re ₀ , −im ₀ , −re ₁]

y ₃=[x ₀ , jx ₀ , −x ₀ , −jx ₀]=[re ₀ , im ₀ , re ₁ , j˜re ₀, j·im₀ , j·re ₁ , −re ₀ , −im ₀ , −re ₁ , −j·re ₀ , −j·im ₀ , −j·re ₁]

For M values other than 12, particular embodiments may use another sequence x₀, e.g. for M=24 an x₀ sequence of length 6 may be used. For L=4, the same block-spreading sequence (based on DFT(4) matrix) may be used.

The block spreading by DFT(4) matrix means that all above y_(i) occupy different frequency-domain combs with a comb width of L=4. If the pulse shaper implements a cyclic convolution, the comb structure is even maintained after the pulse shaping.

A particular advantage of pi/BPSK is that zero crossing is avoided. This means that a transition 1→−1 from one to the next symbol is avoided. In y₀ and y₂ above, at the shaded symbol positions, the signaling alphabet does not change between the adjacent symbols, but instead re₁, re₀(in y₀) and re₁, −re₀ (in y₂) is used. If sign(re₀)=sign(re₁) (which implies re₀=re₁ for BPSK), a zero-crossing is avoided in y₀ but forced in y₂. Alternatively, with sign(re₀)=−sign(re₁) is zero-crossing is avoided in y₂ but forced in y₀.

Also, in some particular embodiments, it may be preferable if the last sample of a DM-RS sequence is from a different signaling alphabet than the first sample of the DM-RS sequence to avoid zero crossings at the cyclic prefix boundary. While y₁ and y₂ fulfill that, first and last samples of y₀ and y₂ are taken from the same signaling alphabet. However, the same restrictions on re₀ and re₁ as discussed above also solve this problem. Specifically, the first and last samples of the DM-RS sequence belong to the same signaling alphabet but have the same sign avoid zero crossings.

In total, only three DM-RS can be generated that are both orthogonal using different combs and avoid zero crossing. The DM-RS set with L=4 can either be limited to three sequences (by excluding y₀ or y₂ and enforcing a relationship on re₀ and re₁ that avoids zero crossing). Alternatively, the set can contain four DM-RS sequences but one of them has a zero crossing and, thus, higher PAPR/CM. The DM-RS with zero crossing could be assigned to a UE with better link budget.

Another possibility is to set either re₀ or re₁ to zero. This also avoids zero crossings. However, setting sequence elements to zero decreases average power while it does not reduce peak values. The PAPR/CM of such a design will, therefore, be worse. While such a design is possible, it may be a less preferred embodiment.

Above problem occurs for all x₀ of odd length (to obtain an M of 12, 36, . . . with L=4). For x₀ of even length (to obtain an M of 24, 48, . . . with L=4) a similar problem occurs for y₁ and y₃, only one of them can be constructed without zero crossing.

In the examples described above, the sequences y₀, y₁, y₂ and y₃ are all constructed from the sequence x₀, but in general each sequence y_(i) can be associated with an x_(i) where x₀, x₁, x₂ and x₃ represent different sequences. Thus, in particular embodiments the case with L=4 yields:

y ₀=[x ₀ ,x ₀ ,x ₀ ,x ₀], y ₁=[x ₁ ,−jx ₁ ,−x ₁ ,jx ₁], y ₂=[x ₂ ,−x ₂ ,x ₂ ,−x ₂], y ₃=[x ₃ ,−jx ₃ ,−x ₃ ,jx ₃].

In particular embodiments, the sequences x_(i) may refer to pseudo-random sequences, for example, derived from a length-31 Gold sequence design, or for smaller M it could refer to computer-optimized pi/2 BPSK sequences to obtain desirable properties such as low PAPR/CM and low cross-correlations.

In particular embodiments, the sequences x_(i) may be UE-specific or be associated with a cell ID, and in principle refer to any type of sequences with desirable properties, even Zadoff-Chu sequences. Orthogonality between different DM-RS can be obtained via frequency division modulation FDM (different combs) and (pseudo-)orthogonality can be obtained between DM-RS on the same comb with x_(i) sequences with sufficiently low cross correlation.

Associating different x_(i) with different y_(i) is not limited to L=4, it is also applicable to other L values.

Some embodiments may include multiplexing with regular (non-pi/2 BPSK) DFTS-OFDM or OFDM based PUSCH. Regular DFTS-OFDM and OFDM based PUSCH use DM-RS that are mapped to a comb 2. To multiplex pi/2 BPSK DFTS-OFDM based PUSCH with regular DFTS-OFDM or OFDM based PUSCH, DM-RS of pi/2 BPSK DFTS-OFDM based PUSCH must occupy one comb-2 while the other comb-2 is used by regular DFTS-OFDM or OFDM DM-RS.

With L=2 two combs are generated, one is used by DM-RS of pi/2 BPSK DFTS-OFDM based PUSCH and the other comb by DM-RS of DFTS-OFDM or OFDM based PUSCH.

With L=4 four combs are generated. If DM-RS of regular DFTS-OFDM or OFDM based PUSCH occupy even subcarriers, DM-RS of pi/2 BPSK DFTS-OFDM based PUSCH must occupy odd subcarriers. For example, y₁ and y₂ may occupy odd subcarriers (y₁: subcarriers 3, 7, 11 in a PRB; y₃: subcarriers 1, 5, 9 in a PRB, first subcarrier in a PRB is subcarrier 0) so y₁ and y₃ can be multiplexed with other DM-RS types occupying even subcarriers.

If DM-RS of regular DFTS-OFDM or OFDM based PUSCH occupy odd subcarriers, DM-RS of pi/2 BPSK DFTS-OFDM based PUSCH must occupy even subcarriers. Thus, continuing the above example, y₀ and y₂ occupy even subcarriers (y₀: subcarriers 0, 4, 8 in a PRB; y₂: subcarriers 2, 6, 10 in a PRB, first subcarrier in a PRB is subcarrier 0) so y₀ and y₂ can be multiplexed with other DM-RS types occupying odd subcarriers.

Above it was shown for L=4 (depending on M and thus on length of x₀) that for one of the combs only one DM-RS can be constructed that avoids zero crossings. It is preferable that this comb is not used by DM-RS of pi/2 BPSK DFTS-OFDM based PUSCH but is assigned to DM-RS of regular DFTS-OFDM of OFDM based PUSCH. DM-RS of pi/2 BPSK DFTS-OFDM based PUSCH preferable use that comb where both sequences avoid zero crossings.

Which comb to multiplex DM-RS of pi/2 BPSK on may be dynamically configured via DCI, where the considered comb is either explicitly indicated or implicitly given by indicating the DFT block-code

(L=2:{[1,1], [1, −1]}: L=4:{[1, 1, 1, 1], [1, −j, −1, j], [1, −1, 1, −1], [1,j, −1, −j]})

In a system supporting multiple comb structure, L may be configured by higher layer signaling.

Some embodiments include discontinuities at DFTS-OFDM symbol boundaries. Another potential source of large waveform discontinuities is at the DFTS-OFDM symbol boundary between the end of a previous DFTS-OFDM symbol and the cyclic prefix beginning of the current DFTS-OFDM symbol. FIG. 3 illustrates that the first sample or first few samples of a cyclic prefix are either set to zero or are a function of the last or last few samples of the previous DFTS-OFDM symbol.

In a particular embodiment, to make this transition smoother, the first sample or the first few samples of a cyclic prefix are set to zero. Another alternative is to set the first sample or first few samples of a cyclic prefix as a function of the last sample or last few samples of the previous DFTS-OFDM symbol to smoothen the waveform. It is not necessary to combine the particular embodiment with any other embodiments described herein.

FIG. 4 illustrates a wireless network, according to certain embodiments. Although the subject matter described herein may be implemented in any appropriate type of system using any suitable components, the embodiments disclosed herein are described in relation to a wireless network, such as the example wireless network illustrated in FIG. 4. For simplicity, the wireless network of FIG. 4 only depicts network 106, network nodes 160 and 160 b, and WDs 110, 110 b, and 110 c. In practice, a wireless network may further include any additional elements suitable to support communication between wireless devices or between a wireless device and another communication device, such as a landline telephone, a service provider, or any other network node or end device. Of the illustrated components, network node 160 and wireless device (WD) 110 are depicted with additional detail. The wireless network may provide communication and other types of services to one or more wireless devices to facilitate the wireless devices' access to and/or use of the services provided by, or via, the wireless network.

The wireless network may comprise and/or interface with any type of communication, telecommunication, data, cellular, and/or radio network or other similar type of system. In some embodiments, the wireless network may be configured to operate according to specific standards or other types of predefined rules or procedures. Thus, particular embodiments of the wireless network may implement communication standards, such as Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), and/or other suitable 2G, 3G, 4G, or 5G standards; wireless local area network (WLAN) standards, such as the IEEE 802.11 standards; and/or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave and/or ZigBee standards.

Network 106 may comprise one or more backhaul networks, core networks, IP networks, public switched telephone networks (PSTNs), packet data networks, optical networks, wide-area networks (WANs), local area networks (LANs), wireless local area networks (WLANs), wired networks, wireless networks, metropolitan area networks, and other networks to enable communication between devices.

Network node 160 and WD 110 comprise various components described in more detail below. These components work together in order to provide network node and/or wireless device functionality, such as providing wireless connections in a wireless network. In different embodiments, the wireless network may comprise any number of wired or wireless networks, network nodes, base stations, controllers, wireless devices, relay stations, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections.

As used herein, network node refers to equipment capable, configured, arranged and/or operable to communicate directly or indirectly with a wireless device and/or with other network nodes or equipment in the wireless network to enable and/or provide wireless access to the wireless device and/or to perform other functions (e.g., administration) in the wireless network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)). Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and may then also be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units and/or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS). Yet further examples of network nodes include multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell/multicast coordination entities (MCEs), core network nodes (e.g., MSCs, MMEs), O&M nodes, OSS nodes, SON nodes, positioning nodes (e.g., E-SMLCs), and/or MDTs. As another example, a network node may be a virtual network node as described in more detail below. More generally, however, network nodes may represent any suitable device (or group of devices) capable, configured, arranged, and/or operable to enable and/or provide a wireless device with access to the wireless network or to provide some service to a wireless device that has accessed the wireless network.

FIG. 5 illustrates an example network node 160, according to certain embodiments. As depicted, network node 160 includes processing circuitry 170, device readable medium 180, interface 190, auxiliary equipment 184, power source 186, power circuitry 187, and antenna 162. Although network node 160 illustrated in the example wireless network of FIG. 4 may represent a device that includes the illustrated combination of hardware components, other embodiments may comprise network nodes with different combinations of components. It is to be understood that a network node comprises any suitable combination of hardware and/or software needed to perform the tasks, features, functions and methods disclosed herein. Moreover, while the components of network node 160 are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, a network node may comprise multiple different physical components that make up a single illustrated component (e.g., device readable medium 180 may comprise multiple separate hard drives as well as multiple RAM modules).

Similarly, network node 160 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which network node 160 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeB's. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, network node 160 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate device readable medium 180 for the different RATs) and some components may be reused (e.g., the same antenna 162 may be shared by the RATs). Network node 160 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 160, such as, for example, GSM, WCDMA, LTE, NR, WiFi, or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 160.

Processing circuitry 170 is configured to perform any determining, calculating, or similar operations (e.g., certain obtaining operations) described herein as being provided by a network node. These operations performed by processing circuitry 170 may include processing information obtained by processing circuitry 170 by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and/or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination.

Processing circuitry 170 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node 160 components, such as device readable medium 180, network node 160 functionality. For example, processing circuitry 170 may execute instructions stored in device readable medium 180 or in memory within processing circuitry 170. Such functionality may include providing any of the various wireless features, functions, or benefits discussed herein. In some embodiments, processing circuitry 170 may include a system on a chip (SOC).

In some embodiments, processing circuitry 170 may include one or more of radio frequency (RF) transceiver circuitry 172 and baseband processing circuitry 174. In some embodiments, radio frequency (RF) transceiver circuitry 172 and baseband processing circuitry 174 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 172 and baseband processing circuitry 174 may be on the same chip or set of chips, boards, or units

In certain embodiments, some or all of the functionality described herein as being provided by a network node, base station, eNB or other such network device may be performed by processing circuitry 170 executing instructions stored on device readable medium 180 or memory within processing circuitry 170. In alternative embodiments, some or all of the functionality may be provided by processing circuitry 170 without executing instructions stored on a separate or discrete device readable medium, such as in a hard-wired manner. In any of those embodiments, whether executing instructions stored on a device readable storage medium or not, processing circuitry 170 can be configured to perform the described functionality. The benefits provided by such functionality are not limited to processing circuitry 170 alone or to other components of network node 160, but are enjoyed by network node 160 as a whole, and/or by end users and the wireless network generally.

Device readable medium 180 may comprise any form of volatile or non-volatile computer readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device readable and/or computer-executable memory devices that store information, data, and/or instructions that may be used by processing circuitry 170. Device readable medium 180 may store any suitable instructions, data or information, including a computer program, software, an application including one or more of logic, rules, code, tables, etc. and/or other instructions capable of being executed by processing circuitry 170 and, utilized by network node 160. Device readable medium 180 may be used to store any calculations made by processing circuitry 170 and/or any data received via interface 190. In some embodiments, processing circuitry 170 and device readable medium 180 may be considered to be integrated.

Interface 190 is used in the wired or wireless communication of signalling and/or data between network node 160, network 106, and/or WDs 110. As illustrated, interface 190 comprises port(s)/terminal(s) 194 to send and receive data, for example to and from network 106 over a wired connection. Interface 190 also includes radio front end circuitry 192 that may be coupled to, or in certain embodiments a part of, antenna 162. Radio front end circuitry 192 comprises filters 198 and amplifiers 196. Radio front end circuitry 192 may be connected to antenna 162 and processing circuitry 170. Radio front end circuitry may be configured to condition signals communicated between antenna 162 and processing circuitry 170. Radio front end circuitry 192 may receive digital data that is to be sent out to other network nodes or WDs via a wireless connection. Radio front end circuitry 192 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 198 and/or amplifiers 196. The radio signal may then be transmitted via antenna 162. Similarly, when receiving data, antenna 162 may collect radio signals which are then converted into digital data by radio front end circuitry 192. The digital data may be passed to processing circuitry 170. In other embodiments, the interface may comprise different components and/or different combinations of components.

In certain alternative embodiments, network node 160 may not include separate radio front end circuitry 192, instead, processing circuitry 170 may comprise radio front end circuitry and may be connected to antenna 162 without separate radio front end circuitry 192. Similarly, in some embodiments, all or some of RF transceiver circuitry 172 may be considered a part of interface 190. In still other embodiments, interface 190 may include one or more ports or terminals 194, radio front end circuitry 192, and RF transceiver circuitry 172, as part of a radio unit (not shown), and interface 190 may communicate with baseband processing circuitry 174, which is part of a digital unit (not shown).

Antenna 162 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. Antenna 162 may be coupled to radio front end circuitry 190 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In some embodiments, antenna 162 may comprise one or more omni-directional, sector or panel antennas operable to transmit/receive radio signals between, for example, 2 GHz and 66 GHz. An omni-directional antenna may be used to transmit/receive radio signals in any direction, a sector antenna may be used to transmit/receive radio signals from devices within a particular area, and a panel antenna may be a line of sight antenna used to transmit/receive radio signals in a relatively straight line. In some instances, the use of more than one antenna may be referred to as MIMO. In certain embodiments, antenna 162 may be separate from network node 160 and may be connectable to network node 160 through an interface or port.

Antenna 162, interface 190, and/or processing circuitry 170 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by a network node. Any information, data and/or signals may be received from a wireless device, another network node and/or any other network equipment. Similarly, antenna 162, interface 190, and/or processing circuitry 170 may be configured to perform any transmitting operations described herein as being performed by a network node. Any information, data and/or signals may be transmitted to a wireless device, another network node and/or any other network equipment.

Power circuitry 187 may comprise, or be coupled to, power management circuitry and is configured to supply the components of network node 160 with power for performing the functionality described herein. Power circuitry 187 may receive power from power source 186. Power source 186 and/or power circuitry 187 may be configured to provide power to the various components of network node 160 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). Power source 186 may either be included in, or external to, power circuitry 187 and/or network node 160. For example, network node 160 may be connectable to an external power source (e.g., an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry 187. As a further example, power source 186 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry 187. The battery may provide backup power should the external power source fail. Other types of power sources, such as photovoltaic devices, may also be used.

Alternative embodiments of network node 160 may include additional components beyond those shown in FIG. 5 that may be responsible for providing certain aspects of the network node's functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein. For example, network node 160 may include user interface equipment to allow input of information into network node 160 and to allow output of information from network node 160. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for network node 160.

FIG. 6 illustrates an example wireless device (WD), according to certain embodiments. As used herein, WD refers to a device capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other wireless devices. Unless otherwise noted, the term WD may be used interchangeably herein with user equipment (UE). Communicating wirelessly may involve transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information through air. In some embodiments, a WD may be configured to transmit and/or receive information without direct human interaction. For instance, a WD may be designed to transmit information to a network on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the network. Examples of a WD include, but are not limited to, a smart phone, a mobile phone, a cell phone, a voice over IP (VoIP) phone, a wireless local loop phone, a desktop computer, a personal digital assistant (PDA), a wireless cameras, a gaming console or device, a music storage device, a playback appliance, a wearable terminal device, a wireless endpoint, a mobile station, a tablet, a laptop, a laptop-embedded equipment (LEE), a laptop-mounted equipment (LME), a smart device, a wireless customer-premise equipment (CPE). a vehicle-mounted wireless terminal device, etc. A WD may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-everything (V2X) and may in this case be referred to as a D2D communication device. As yet another specific example, in an Internet of Things (IoT) scenario, a WD may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another WD and/or a network node. The WD may in this case be a machine-to-machine (M2M) device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the WD may be a UE implementing the 3GPP narrow band internet of things (NB-IoT) standard. Particular examples of such machines or devices are sensors, metering devices such as power meters, industrial machinery, or home or personal appliances (e.g. refrigerators, televisions, etc.) personal wearables (e.g., watches, fitness trackers, etc.). In other scenarios, a WD may represent a vehicle or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation. A WD as described above may represent the endpoint of a wireless connection, in which case the device may be referred to as a wireless terminal. Furthermore, a WD as described above may be mobile, in which case it may also be referred to as a mobile device or a mobile terminal.

As illustrated in FIG. 6, wireless device 110 includes antenna 111, interface 114, processing circuitry 120, device readable medium 130, user interface equipment 132, auxiliary equipment 134, power source 136 and power circuitry 137. WD 110 may include multiple sets of one or more of the illustrated components for different wireless technologies supported by WD 110, such as, for example, GSM, WCDMA, LTE, NR, WiFi, WiMAX, or Bluetooth wireless technologies, just to mention a few. These wireless technologies may be integrated into the same or different chips or set of chips as other components within WD 110.

Antenna 111 may include one or more antennas or antenna arrays, configured to send and/or receive wireless signals, and is connected to interface 114. In certain alternative embodiments, antenna 111 may be separate from WD 110 and be connectable to WD 110 through an interface or port. Antenna 111, interface 114, and/or processing circuitry 120 may be configured to perform any receiving or transmitting operations described herein as being performed by a WD. Any information, data and/or signals may be received from a network node and/or another WD. In some embodiments, radio front end circuitry and/or antenna 111 may be considered an interface.

As illustrated, interface 114 comprises radio front end circuitry 112 and antenna 111. Radio front end circuitry 112 comprise one or more filters 118 and amplifiers 116. Radio front end circuitry 114 is connected to antenna 111 and processing circuitry 120, and is configured to condition signals communicated between antenna 111 and processing circuitry 120. Radio front end circuitry 112 may be coupled to or a part of antenna 111. In some embodiments, WD 110 may not include separate radio front end circuitry 112; rather, processing circuitry 120 may comprise radio front end circuitry and may be connected to antenna 111. Similarly, in some embodiments, some or all of RF transceiver circuitry 122 may be considered a part of interface 114. Radio front end circuitry 112 may receive digital data that is to be sent out to other network nodes or WDs via a wireless connection. Radio front end circuitry 112 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 118 and/or amplifiers 116. The radio signal may then be transmitted via antenna 111. Similarly, when receiving data, antenna 111 may collect radio signals which are then converted into digital data by radio front end circuitry 112. The digital data may be passed to processing circuitry 120. In other embodiments, the interface may comprise different components and/or different combinations of components.

Processing circuitry 120 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software, and/or encoded logic operable to provide, either alone or in conjunction with other WD 110 components, such as device readable medium 130, WD 110 functionality. Such functionality may include providing any of the various wireless features or benefits discussed herein. For example, processing circuitry 120 may execute instructions stored in device readable medium 130 or in memory within processing circuitry 120 to provide the functionality disclosed herein.

As illustrated, processing circuitry 120 includes one or more of RF transceiver circuitry 122, baseband processing circuitry 124, and application processing circuitry 126. In other embodiments, the processing circuitry may comprise different components and/or different combinations of components. In certain embodiments processing circuitry 120 of WD 110 may comprise a SOC. In some embodiments, RF transceiver circuitry 122, baseband processing circuitry 124, and application processing circuitry 126 may be on separate chips or sets of chips. In alternative embodiments, part or all of baseband processing circuitry 124 and application processing circuitry 126 may be combined into one chip or set of chips, and RF transceiver circuitry 122 may be on a separate chip or set of chips. In still alternative embodiments, part or all of RF transceiver circuitry 122 and baseband processing circuitry 124 may be on the same chip or set of chips, and application processing circuitry 126 may be on a separate chip or set of chips. In yet other alternative embodiments, part or all of RF transceiver circuitry 122, baseband processing circuitry 124, and application processing circuitry 126 may be combined in the same chip or set of chips. In some embodiments, RF transceiver circuitry 122 may be a part of interface 114. RF transceiver circuitry 122 may condition RF signals for processing circuitry 120.

In certain embodiments, some or all of the functionality described herein as being performed by a WD may be provided by processing circuitry 120 executing instructions stored on device readable medium 130, which in certain embodiments may be a computer-readable storage medium. In alternative embodiments, some or all of the functionality may be provided by processing circuitry 120 without executing instructions stored on a separate or discrete device readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a device readable storage medium or not, processing circuitry 120 can be configured to perform the described functionality. The benefits provided by such functionality are not limited to processing circuitry 120 alone or to other components of WD 110, but are enjoyed by WD 110 as a whole, and/or by end users and the wireless network generally.

Processing circuitry 120 may be configured to perform any determining, calculating, or similar operations (e.g., certain obtaining operations) described herein as being performed by a WD. These operations, as performed by processing circuitry 120, may include processing information obtained by processing circuitry 120 by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored by WD 110, and/or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination.

Device readable medium 130 may be operable to store a computer program, software, an application including one or more of logic, rules, code, tables, etc. and/or other instructions capable of being executed by processing circuitry 120. Device readable medium 130 may include computer memory (e.g., Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (e.g., a hard disk), removable storage media (e.g., a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device readable and/or computer executable memory devices that store information, data, and/or instructions that may be used by processing circuitry 120. In some embodiments, processing circuitry 120 and device readable medium 130 may be considered to be integrated.

User interface equipment 132 may provide components that allow for a human user to interact with WD 110. Such interaction may be of many forms, such as visual, audial, tactile, etc. User interface equipment 132 may be operable to produce output to the user and to allow the user to provide input to WD 110. The type of interaction may vary depending on the type of user interface equipment 132 installed in WD 110. For example, if WD 110 is a smart phone, the interaction may be via a touch screen; if WD 110 is a smart meter, the interaction may be through a screen that provides usage (e.g., the number of gallons used) or a speaker that provides an audible alert (e.g., if smoke is detected). User interface equipment 132 may include input interfaces, devices and circuits, and output interfaces, devices and circuits.

User interface equipment 132 is configured to allow input of information into WD 110, and is connected to processing circuitry 120 to allow processing circuitry 120 to process the input information. User interface equipment 132 may include, for example, a microphone, a proximity or other sensor, keys/buttons, a touch display, one or more cameras, a USB port, or other input circuitry. User interface equipment 132 is also configured to allow output of information from WD 110, and to allow processing circuitry 120 to output information from WD 110. User interface equipment 132 may include, for example, a speaker, a display, vibrating circuitry, a USB port, a headphone interface, or other output circuitry. Using one or more input and output interfaces, devices, and circuits, of user interface equipment 132, WD 110 may communicate with end users and/or the wireless network, and allow them to benefit from the functionality described herein.

Auxiliary equipment 134 is operable to provide more specific functionality which may not be generally performed by WDs. This may comprise specialized sensors for doing measurements for various purposes, interfaces for additional types of communication such as wired communications etc. The inclusion and type of components of auxiliary equipment 134 may vary depending on the embodiment and/or scenario.

Power source 136 may, in some embodiments, be in the form of a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic devices or power cells, may also be used. WD 110 may further comprise power circuitry 137 for delivering power from power source 136 to the various parts of WD 110 which need power from power source 136 to carry out any functionality described or indicated herein. Power circuitry 137 may in certain embodiments comprise power management circuitry. Power circuitry 137 may additionally or alternatively be operable to receive power from an external power source; in which case WD 110 may be connectable to the external power source (such as an electricity outlet) via input circuitry or an interface such as an electrical power cable. Power circuitry 137 may also in certain embodiments be operable to deliver power from an external power source to power source 136. This may be, for example, for the charging of power source 136. Power circuitry 137 may perform any formatting, converting, or other modification to the power from power source 136 to make the power suitable for the respective components of WD 110 to which power is supplied.

FIG. 7 illustrates an example UE, according to certain embodiments. As used herein, a UE may not necessarily have a user in the sense of a human user who owns and/or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter). UE 200 may be any UE identified by the 3^(rd) Generation Partnership Project (3GPP), including a NB-IoT UE, a machine type communication (MTC) UE, and/or an enhanced MTC (eMTC) UE. UE 200, as illustrated in FIG. 7, is one example of a WD configured for communication in accordance with one or more communication standards promulgated by the 3^(rd) Generation Partnership Project (3GPP), such as 3GPP's GSM, UMTS, LTE, and/or 5G standards. As mentioned previously, the term WD and UE may be used interchangeable. Accordingly, although FIG. 7 is a UE, the components discussed herein are equally applicable to a WD, and vice-versa.

In FIG. 7, UE 200 includes processing circuitry 201 that is operatively coupled to input/output interface 205, radio frequency (RF) interface 209, network connection interface 211, memory 215 including random access memory (RAM) 217, read-only memory (ROM) 219, and storage medium 221 or the like, communication subsystem 231, power source 233, and/or any other component, or any combination thereof. Storage medium 221 includes operating system 223, application program 225, and data 227. In other embodiments, storage medium 221 may include other similar types of information. Certain UEs may utilize all of the components shown in FIG. 7, or only a subset of the components. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

In FIG. 7, processing circuitry 201 may be configured to process computer instructions and data. Processing circuitry 201 may be configured to implement any sequential state machine operative to execute machine instructions stored as machine-readable computer programs in the memory, such as one or more hardware-implemented state machines (e.g., in discrete logic, FPGA, ASIC, etc.); programmable logic together with appropriate firmware; one or more stored program, general-purpose processors, such as a microprocessor or Digital Signal Processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 201 may include two central processing units (CPUs). Data may be information in a form suitable for use by a computer.

In the depicted embodiment, input/output interface 205 may be configured to provide a communication interface to an input device, output device, or input and output device. UE 200 may be configured to use an output device via input/output interface 205. An output device may use the same type of interface port as an input device. For example, a USB port may be used to provide input to and output from UE 200. The output device may be a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. UE 200 may be configured to use an input device via input/output interface 205 to allow a user to capture information into UE 200. The input device may include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, another like sensor, or any combination thereof For example, the input device may be an accelerometer, a magnetometer, a digital camera, a microphone, and an optical sensor.

In FIG. 7, RF interface 209 may be configured to provide a communication interface to RF components such as a transmitter, a receiver, and an antenna. Network connection interface 211 may be configured to provide a communication interface to network 243 a. Network 243 a may encompass wired and/or wireless networks such as a local-area network (LAN), a wide-area network (WAN), a computer network, a wireless network, a telecommunications network, another like network or any combination thereof For example, network 243 a may comprise a Wi-Fi network. Network connection interface 211 may be configured to include a receiver and a transmitter interface used to communicate with one or more other devices over a communication network according to one or more communication protocols, such as Ethernet, TCP/IP, SONET, ATM, or the like. Network connection interface 211 may implement receiver and transmitter functionality appropriate to the communication network links (e.g., optical, electrical, and the like). The transmitter and receiver functions may share circuit components, software or firmware, or alternatively may be implemented separately.

RAM 217 may be configured to interface via bus 202 to processing circuitry 201 to provide storage or caching of data or computer instructions during the execution of software programs such as the operating system, application programs, and device drivers. ROM 219 may be configured to provide computer instructions or data to processing circuitry 201. For example, ROM 219 may be configured to store invariant low-level system code or data for basic system functions such as basic input and output (I/O), startup, or reception of keystrokes from a keyboard that are stored in a non-volatile memory. Storage medium 221 may be configured to include memory such as RAM, ROM, programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, floppy disks, hard disks, removable cartridges, or flash drives. In one example, storage medium 221 may be configured to include operating system 223, application program 225 such as a web browser application, a widget or gadget engine or another application, and data file 227. Storage medium 221 may store, for use by UE 200, any of a variety of various operating systems or combinations of operating systems.

Storage medium 221 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), floppy disk drive, flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as a subscriber identity module or a removable user identity (SIM/RUIM) module, other memory, or any combination thereof. Storage medium 221 may allow UE 200 to access computer-executable instructions, application programs or the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied in storage medium 221, which may comprise a device readable medium.

In FIG. 7, processing circuitry 201 may be configured to communicate with network 243 b using communication subsystem 231. Network 243 a and network 243 b may be the same network or networks or different network or networks. Communication subsystem 231 may be configured to include one or more transceivers used to communicate with network 243 b. For example, communication subsystem 231 may be configured to include one or more transceivers used to communicate with one or more remote transceivers of another device capable of wireless communication such as another WD, UE, or base station of a radio access network (RAN) according to one or more communication protocols, such as IEEE 802.2, CDMA, WCDMA, GSM, LTE, UTRAN, WiMax, or the like. Each transceiver may include transmitter 233 and/or receiver 235 to implement transmitter or receiver functionality, respectively, appropriate to the RAN links (e.g., frequency allocations and the like). Further, transmitter 233 and receiver 235 of each transceiver may share circuit components, software or firmware, or alternatively may be implemented separately.

In the illustrated embodiment, the communication functions of communication subsystem 231 may include data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof For example, communication subsystem 231 may include cellular communication, Wi-Fi communication, Bluetooth communication, and GPS communication. Network 243 b may encompass wired and/or wireless networks such as a local-area network (LAN), a wide-area network (WAN), a computer network, a wireless network, a telecommunications network, another like network or any combination thereof For example, network 243 b may be a cellular network, a Wi-Fi network, and/or a near-field network. Power source 213 may be configured to provide alternating current (AC) or direct current (DC) power to components of UE 200.

The features, benefits and/or functions described herein may be implemented in one of the components of UE 200 or partitioned across multiple components of UE 200. Further, the features, benefits, and/or functions described herein may be implemented in any combination of hardware, software or firmware. In one example, communication subsystem 231 may be configured to include any of the components described herein. Further, processing circuitry 201 may be configured to communicate with any of such components over bus 202. In another example, any of such components may be represented by program instructions stored in memory that when executed by processing circuitry 201 perform the corresponding functions described herein. In another example, the functionality of any of such components may be partitioned between processing circuitry 201 and communication subsystem 231. In another example, the non-computationally intensive functions of any of such components may be implemented in software or firmware and the computationally intensive functions may be implemented in hardware.

FIG. 8 illustrates a virtualization environment 300 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to a node (e.g., a virtualized base station or a virtualized radio access node) or to a device (e.g., a UE, a wireless device or any other type of communication device) or components thereof and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components (e.g., via one or more applications, components, functions, virtual machines or containers executing on one or more physical processing nodes in one or more networks).

In some embodiments, some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines implemented in one or more virtual environments 300 hosted by one or more of hardware nodes 330. Further, in embodiments in which the virtual node is not a radio access node or does not require radio connectivity (e.g., a core network node), then the network node may be entirely virtualized.

The functions may be implemented by one or more applications 320 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) operative to implement some of the features, functions, and/or benefits of some of the embodiments disclosed herein. Applications 320 are run in virtualization environment 300 which provides hardware 330 comprising processing circuitry 360 and memory 390. Memory 390 contains instructions 395 executable by processing circuitry 360 whereby application 320 is operative to provide one or more of the features, benefits, and/or functions disclosed herein.

Virtualization environment 300, comprises general-purpose or special-purpose network hardware devices 330 comprising a set of one or more processors or processing circuitry 360, which may be commercial off-the-shelf (COTS) processors, dedicated Application Specific Integrated Circuits (ASICs), or any other type of processing circuitry including digital or analog hardware components or special purpose processors. Each hardware device may comprise memory 390-1 which may be non-persistent memory for temporarily storing instructions 395 or software executed by processing circuitry 360. Each hardware device may comprise one or more network interface controllers (NICs) 370, also known as network interface cards, which include physical network interface 380. Each hardware device may also include non-transitory, persistent, machine-readable storage media 390-2 having stored therein software 395 and/or instructions executable by processing circuitry 360. Software 395 may include any type of software including software for instantiating one or more virtualization layers 350 (also referred to as hypervisors), software to execute virtual machines 340 as well as software allowing it to execute functions, features and/or benefits described in relation with some embodiments described herein.

Virtual machines 340, comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 350 or hypervisor. Different embodiments of the instance of virtual appliance 320 may be implemented on one or more of virtual machines 340, and the implementations may be made in different ways.

During operation, processing circuitry 360 executes software 395 to instantiate the hypervisor or virtualization layer 350, which may sometimes be referred to as a virtual machine monitor (VMM). Virtualization layer 350 may present a virtual operating platform that appears like networking hardware to virtual machine 340.

As shown in FIG. 8, hardware 330 may be a standalone network node with generic or specific components. Hardware 330 may comprise antenna 3225 and may implement some functions via virtualization. Alternatively, hardware 330 may be part of a larger cluster of hardware (e.g. such as in a data center or customer premise equipment (CPE)) where many hardware nodes work together and are managed via management and orchestration (MANO) 3100, which, among others, oversees lifecycle management of applications 320.

Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

In the context of NFV, virtual machine 340 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of virtual machines 340, and that part of hardware 330 that executes that virtual machine, be it hardware dedicated to that virtual machine and/or hardware shared by that virtual machine with others of the virtual machines 340, forms a separate virtual network elements (VNE).

Still in the context of NFV, Virtual Network Function (VNF) is responsible for handling specific network functions that run in one or more virtual machines 340 on top of hardware networking infrastructure 330 and corresponds to application 320 in FIG. 8.

In some embodiments, one or more radio units 3200 that each include one or more transmitters 3220 and one or more receivers 3210 may be coupled to one or more antennas 3225. Radio units 3200 may communicate directly with hardware nodes 330 via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station.

In some embodiments, some signalling can be effected with the use of control system 3230 which may alternatively be used for communication between the hardware nodes 330 and radio units 3200.

FIG. 9 illustrates an example telecommunication network connected via an intermediate network to a host computer, according to certain embodiments. Specifically, in accordance with an example embodiment, a communication system includes telecommunication network 410, such as a 3GPP-type cellular network, which comprises access network 411, such as a radio access network, and core network 414. Access network 411 comprises a plurality of base stations 412 a, 412 b, 412 c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 413 a, 413 b, 413 c. Each base station 412 a, 412 b, 412 c is connectable to core network 414 over a wired or wireless connection 415. A first UE 491 located in coverage area 413 c is configured to wirelessly connect to, or be paged by, the corresponding base station 412 c. A second UE 492 in coverage area 413 a is wirelessly connectable to the corresponding base station 412 a. While a plurality of UEs 491, 492 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 412.

Telecommunication network 410 is itself connected to host computer 430, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. Host computer 430 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. Connections 421 and 422 between telecommunication network 410 and host computer 430 may extend directly from core network 414 to host computer 430 or may go via an optional intermediate network 420. Intermediate network 420 may be one of, or a combination of more than one of, a public, private or hosted network; intermediate network 420, if any, may be a backbone network or the Internet; in particular, intermediate network 420 may comprise two or more sub-networks (not shown).

The communication system of FIG. 9 as a whole enables connectivity between the connected UEs 491, 492 and host computer 430. The connectivity may be described as an over-the-top (OTT) connection 450. Host computer 430 and the connected UEs 491, 492 are configured to communicate data and/or signaling via OTT connection 450, using access network 411, core network 414, any intermediate network 420 and possible further infrastructure (not shown) as intermediaries. OTT connection 450 may be transparent in the sense that the participating communication devices through which OTT connection 450 passes are unaware of routing of uplink and downlink communications. For example, base station 412 may not or need not be informed about the past routing of an incoming downlink communication with data originating from host computer 430 to be forwarded (e.g., handed over) to a connected UE 491. Similarly, base station 412 need not be aware of the future routing of an outgoing uplink communication originating from the UE 491 towards the host computer 430.

FIG. 10 illustrates an example host computer communicating via a base station with a user equipment over a partially wireless connection, according to certain embodiments. Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to FIG. 10. In communication system 500, host computer 510 comprises hardware 515 including communication interface 516 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of communication system 500. Host computer 510 further comprises processing circuitry 518, which may have storage and/or processing capabilities. In particular, processing circuitry 518 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. Host computer 510 further comprises software 511, which is stored in or accessible by host computer 510 and executable by processing circuitry 518. Software 511 includes host application 512. Host application 512 may be operable to provide a service to a remote user, such as UE 530 connecting via OTT connection 550 terminating at UE 530 and host computer 510. In providing the service to the remote user, host application 512 may provide user data which is transmitted using OTT connection 550.

Communication system 500 further includes base station 520 provided in a telecommunication system and comprising hardware 525 enabling it to communicate with host computer 510 and with UE 530. Hardware 525 may include communication interface 526 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of communication system 500, as well as radio interface 527 for setting up and maintaining at least wireless connection 570 with UE 530 located in a coverage area (not shown in FIG. 10) served by base station 520. Communication interface 526 may be configured to facilitate connection 560 to host computer 510. Connection 560 may be direct or it may pass through a core network (not shown in FIG. 10) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, hardware 525 of base station 520 further includes processing circuitry 528, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. Base station 520 further has software 521 stored internally or accessible via an external connection.

Communication system 500 further includes UE 530 already referred to. Its hardware 535 may include radio interface 537 configured to set up and maintain wireless connection 570 with a base station serving a coverage area in which UE 530 is currently located. Hardware 535 of UE 530 further includes processing circuitry 538, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. UE 530 further comprises software 531, which is stored in or accessible by UE 530 and executable by processing circuitry 538. Software 531 includes client application 532. Client application 532 may be operable to provide a service to a human or non-human user via UE 530, with the support of host computer 510. In host computer 510, an executing host application 512 may communicate with the executing client application 532 via OTT connection 550 terminating at UE 530 and host computer 510. In providing the service to the user, client application 532 may receive request data from host application 512 and provide user data in response to the request data. OTT connection 550 may transfer both the request data and the user data. Client application 532 may interact with the user to generate the user data that it provides.

It is noted that host computer 510, base station 520 and UE 530 illustrated in FIG. 10 may be similar or identical to host computer QQ430, one of base stations QQ412 a, QQ412 b, QQ412 c and one of UEs QQ491, QQ492 of Figure QQ4, respectively. This is to say, the inner workings of these entities may be as shown in FIG. 10 and independently, the surrounding network topology may be that of Figure QQ4.

In FIG. 10, OTT connection 550 has been drawn abstractly to illustrate the communication between host computer 510 and UE 530 via base station 520, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from UE 530 or from the service provider operating host computer 510, or both. While OTT connection 550 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

Wireless connection 570 between UE 530 and base station 520 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to UE 530 using OTT connection 550, in which wireless connection 570 forms the last segment. More precisely, the teachings of these embodiments may reduce the PAPR/CM of an uplink DMRS, and thereby provide benefits such as increased bandwidth.

A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring OTT connection 550 between host computer 510 and UE 530, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring OTT connection 550 may be implemented in software 511 and hardware 515 of host computer 510 or in software 531 and hardware 535 of UE 530, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which OTT connection 550 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 511, 531 may compute or estimate the monitored quantities. The reconfiguring of OTT connection 550 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect base station 520, and it may be unknown or imperceptible to base station 520. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating host computer 510's measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that software 511 and 531 causes messages to be transmitted, in particular empty or ‘dummy’ messages, using OTT connection 550 while it monitors propagation times, errors etc.

FIG. 11 is a flowchart illustrating an example method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to FIGS. 9 and 10. For simplicity of the present disclosure, only drawing references to FIG. 11 will be included in this section. In step 610, the host computer provides user data. In substep 611 (which may be optional) of step 610, the host computer provides the user data by executing a host application. In step 620, the host computer initiates a transmission carrying the user data to the UE. In step 630 (which may be optional), the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step 640 (which may also be optional), the UE executes a client application associated with the host application executed by the host computer.

FIG. 12 is a flowchart illustrating another example method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to FIGS. 9 and 10. For simplicity of the present disclosure, only drawing references to FIG. 12 will be included in this section. In step 710 of the method, the host computer provides user data. In an optional substep (not shown) the host computer provides the user data by executing a host application. In step 720, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In step 730 (which may be optional), the UE receives the user data carried in the transmission.

FIG. 13 is a flowchart illustrating another example method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to FIGS. 9 and 10. For simplicity of the present disclosure, only drawing references to FIG. 13 will be included in this section. In step 810 (which may be optional), the UE receives input data provided by the host computer. Additionally or alternatively, in step 820, the UE provides user data. In substep 821 (which may be optional) of step 820, the UE provides the user data by executing a client application. In substep 811 (which may be optional) of step 810, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in substep 830 (which may be optional), transmission of the user data to the host computer. In step 840 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

FIG. 14 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to FIGS. 9 and 10. For simplicity of the present disclosure, only drawing references to FIG. 14 will be included in this section. In step 910 (which may be optional), in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In step 920 (which may be optional), the base station initiates transmission of the received user data to the host computer. In step 930 (which may be optional), the host computer receives the user data carried in the transmission initiated by the base station.

FIG. 15 illustrates an example method 1000 by a wireless device 110, according to certain embodiments. The method begins at step 1010 with a wireless device, such as 110, obtaining (e.g., via DCI) a first spreading function for spreading a first pi/2-BPSK sequence to occupy a subset of carriers in the frequency domain according to any of the embodiments or examples described above.

At step 1020, the wireless device generates a first DMRS by applying the first spreading function to the first pi/2-BPSK sequence. The DMRS is orthogonal to a second DMRS generated by another wireless device using a second pi/2-BPSK sequence or a regular DFTS-OFDM sequence and a second spreading function. The wireless device, such as wireless device 110, may generate the first DMRS according to any of the examples or embodiments described above.

At step 1030, the wireless device transmits the first DMRS to a network node. For example, wireless device 110 may transmit the first DMRS to network node 160.

FIG. 16 illustrates a schematic block diagram of a virtual apparatus 1100 in a wireless network (for example, the wireless network shown in FIG. 4). The virtual apparatus may be implemented in a wireless device (e.g., wireless device 110 shown in FIG. 4). Virtual apparatus 1100 is operable to carry out the example method described with reference to FIG. 15 and possibly any other processes or methods disclosed herein. It is also to be understood that the method of FIG. 15 is not necessarily carried out solely by apparatus 1100. At least some operations of the method can be performed by one or more other entities.

Virtual Apparatus 1100 may comprise processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein, in several embodiments. In some implementations, the processing circuitry may be used to cause generating unit 1110 and transmitting unit 1120, and any other suitable units of virtual apparatus 1100 to perform corresponding functions according one or more embodiments of the present disclosure.

As illustrated in FIG. 16, virtual apparatus 1100 includes generating unit 1110 and transmitting unit 1120. Generating unit 1110 is configured to generate DMRS according to any of the embodiments and examples described above. Transmitting unit 1120 is configured to transmit DMRS to a network node.

FIG. 17 illustrates an example method 1200 by a wireless device 110 for transmitting DMRS, in accordance with certain embodiments. The method begins at step 1210 when wireless device 110 obtains a first spreading function for spreading a first pi/2-BPSK sequence to occupy a first subset of a plurality of subcarriers in a frequency domain. In a particular embodiment, wireless device 110 may receive, from network node 160, information indicating that the wireless device is to use the first spreading function for spreading the first pi/2-BPSK sequence.

In a particular embodiment, the first pi/2 BPSK sequence is of an even length. Additionally or alternatively, the first pi/2-BPSK sequence has a length of M/L, where M is a size of a DFT precoder performing the DFT precoding and L is a comb distance in the frequency domain.

In a particular embodiment, the first subset of the plurality of subcarriers in the frequency domain includes a frequency-domain comb that is less than an entire set of the plurality of subcarriers.

At step 1220, wireless device 110 generates a first DMRS by applying the first spreading function to the first pi/2-BPSK sequence. In a particular embodiment, the first spreading function includes a block spreading sequence.

In a particular embodiment, wireless device 110 may perform DFT precoding.

At step 1230, wireless device 110 transmits the first DMRS to a network node. In a particular embodiment, for example, transmitting the DMRS includes applying bandwidth controlling processing. The bandwidth controlling processing includes PAPR controlling processing or pulse-shaping processing or cyclic convolution.

In a particular embodiment, the first DMRS is orthogonal to a second DMRS that occupies a second subset of the plurality of characters in the frequency domain. In a particular embodiment, the second DMRS may be generated by the same wireless device that generated the first DMRS (i.e., first wireless device). In another embodiment, the second DMRS may be generated by a wireless device other than the first wireless device.

For example, in a further particular embodiment, the second DMRS may be generated using a second spreading function for spreading a second pi/2-BPSK sequence. In a particular embodiment, the first and second pi/2-BPSK sequences coincide.

As another example, in a further particular embodiment, the second DMRS may be generated using OFDM or regular DFTS-OFDM. Thus, it is possible to multiplex pi/2 PBSK DMRS and DMRS of OFDM or regular DFTS-OFDM. In such an example embodiment, the DMRS may occupy the second subset of the plurality of subcarriers though no spreading is involved in the construction.

In a particular embodiment, the first subset of the plurality of subcarriers over which the first DMRS is mapped comprises a plurality of odd subcarriers within the plurality of subcarriers. A second subset of a plurality of subcarriers over which the second DMRS is spread comprises a plurality of even subcarriers within the plurality of subcarriers.

In a particular embodiment, the first DMRS comprises symbols from at least two alphabets. Additionally, a restriction may be applied to the DMRS after spreading (and prior to cyclic prefix insertion) that a first element and a last element of the first DMRS are 1) from different alphabets within the at least two alphabets or 2) from the same alphabet and of the same sign. For example, the at least two alphabets may include a first alphabet that is {+1 −1} and a second alphabet that is {+j −j}.

FIG. 18 illustrates a schematic block diagram of a virtual apparatus 1300 in a wireless network (for example, the wireless network shown in FIG. 4). The virtual apparatus may be implemented in a wireless device (e.g., wireless device 110 shown in FIG. 4). Virtual apparatus 1300 is operable to carry out the example method described with reference to FIG. 17 and possibly any other processes or methods disclosed herein. It is also to be understood that the method of FIG. 17 is not necessarily carried out solely by apparatus 1300. At least some operations of the method can be performed by one or more other entities.

Virtual Apparatus 1300 may comprise processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein, in several embodiments. In some implementations, the processing circuitry may be used to cause obtaining unit 1310, generating unit 1320, and transmitting unit 1330, and any other suitable units of virtual apparatus 1300 to perform corresponding functions according one or more embodiments of the present disclosure.

As illustrated in FIG. 18, virtual apparatus 1300 includes obtaining unit 1310, generating unit 1320, and transmitting unit 1330. Obtaining unit 1310 is configured to obtain a first spreading function for spreading a first pi/2-BPSK sequence to occupy a first subset of a plurality of subcarriers in a frequency domain. Generating unit 1320 is configured to generate a first DMRS by applying the first spreading function to the first pi/2-BPSK sequence according to any of the embodiments and examples described above. Transmitting unit 1330 is configured to transmit the first DMRS to a network node.

FIG. 19 depicts a method 1400 in accordance with particular embodiments. The method begins at step 1910 with a network node, such as 160, that receives a first DMRS generated using a first block spreading sequence on a pi/2-BPSK sequence such that the first DMRS occupies a first frequency comb according to any of the embodiments or examples described above.

At step 1420, the network node receives a second DMRS orthogonal to the first DRMS and occupying a second frequency comb. The second DMRS may be another pi/2-BPSK sequence or another sequence transmitted using DFTS-OFDM or OFDM. The network node, such as network node 160, may receive the second DMRS generated according to any of the examples or embodiments described above.

FIG. 20 illustrates a schematic block diagram of a virtual apparatus 1500 in a wireless network (for example, the wireless network shown in FIG. 4). The virtual apparatus may be implemented in a network node (e.g., network node160 shown in FIG. 4). Virtual apparatus 1500 is operable to carry out the example method described with reference to FIG. 19 and possibly any other processes or methods disclosed herein. It is also to be understood that the method of FIG. 19 is not necessarily carried out solely by virtual apparatus 1500. At least some operations of the method can be performed by one or more other entities.

Virtual Apparatus 1500 may comprise processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein, in several embodiments. In some implementations, the processing circuitry may be used to cause receiving unit 1510, and any other suitable units of apparatus 1500 to perform corresponding functions according one or more embodiments of the present disclosure.

As illustrated in FIG. 20, virtual apparatus 1500 includes receiving unit 1510. Receiving unit 1510 is configured to receive DMRS generated according to any of the embodiments and examples described above.

The term unit may have conventional meaning in the field of electronics, electrical devices and/or electronic devices and may include, for example, electrical and/or electronic circuitry, devices, modules, processors, memories, logic solid state and/or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and/or displaying functions, and so on, as such as those that are described herein.

FIG. 21 illustrates an exemplary method 1600 by network node 160 for receiving DMRS, in accordance with certain embodiments. The method begins at step 1610 when network node 160 receives a first DMRS generated using a first spreading function applied to a first pi/2-BPSK sequence such that the first DMRS occupies a first frequency comb. The frequency comb includes a first subset of a plurality of subcarriers in the frequency domain.

In a particular embodiment, the first spreading function includes a block spreading function. In a further particular embodiment, the first DMRS was pulse shaped with a cyclic convolution maintaining the first frequency comb. Additionally or alternatively, in a particular embodiment, the first pi/2-BPSK sequence has a length of M/L, where M is a size of a DFT precoder performing the DFT precoding and L is a comb distance in the frequency domain.

In a particular embodiment, the first DMRS comprises symbols from at least two alphabets. Additionally, a restriction may be applied by the transmitting wireless device to the DMRS after spreading (and prior to cyclic prefix insertion) that a first element and a last element of the first DMRS are 1) from different alphabets within the at least two alphabets or 2) from the same alphabet and of the same sign. For example, the at least two alphabets may include a first alphabet that is {+1 −1} and a second alphabet that is {+j −j}.

At step 1620, network node 160 receives a second DMRS occupying a second frequency comb. The second frequency comb includes a second subset of the plurality of subcarriers in the frequency domain. In a particular embodiment, the second DMRS may generated by the wireless device. In another embodiment, the second DMRS is generated by a wireless device other than the first wireless device.

In a particular embodiment, the second DMRS was generated using a second spreading function for spreading a second pi/2-BPSK sequence. In a further particular embodiment, the first and second pi/2-BPSK sequences coincide.

In another particular embodiment, the second DMRS was generated using OFDM or regular DFTS-OFDM.

In a particular embodiment, network node 160 transmits, to first wireless device 110, information indicating that the wireless device is to use a first spreading function for spreading the first pi/2-BPSK sequence to occupy the first subset of the plurality of carriers in the frequency domain. The first DMRS may be received from the first wireless device in response to transmitting the information indicating that the wireless device is to use the first spreading function.

In a particular embodiment, the second DMRS is received from the first wireless device. In another embodiment, the second DMRS is received from a second wireless device.

In a particular embodiment, the method may further include the network node 160 transmitting, to first wireless device 110 or the second wireless device 110, information indicating that the first wireless device 110 or the second wireless device 110 is to use a second spreading function for spreading a second pi/2-BPSK sequence to occupy the second subset of the plurality of subcarriers in the frequency domain. The second DMRS may be received from the first wireless device or the second wireless device in response to transmitting the information indicating that the first wireless device 110 or the second wireless device 110 is to use the second spreading function.

FIG. 22 illustrates a schematic block diagram of a virtual apparatus 1700 in a wireless network (for example, the wireless network shown in FIG. 4). The virtual apparatus may be implemented in a network node (e.g., network node 160 shown in FIG. 4). Virtual apparatus 1700 is operable to carry out the example method described with reference to FIG. 21 and possibly any other processes or methods disclosed herein. It is also to be understood that the method of FIG. 21 is not necessarily carried out solely by apparatus 1700. At least some operations of the method can be performed by one or more other entities.

Virtual Apparatus 1700 may comprise processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein, in several embodiments. In some implementations, the processing circuitry may be used to cause first receiving unit 1710 and second receiving unit 1720 and any other suitable units of virtual apparatus 1700 to perform corresponding functions according one or more embodiments of the present disclosure.

As illustrated in FIG. 22, virtual apparatus 1700 includes first receiving unit 1710 and second receiving unit 1720. First receiving unit 1710 is configured to receive a first DMRS generated using a first spreading function applied to a first pi/2-BPSK sequence such that the first DMRS occupies a first frequency comb. The frequency comb includes a first subset of a plurality of subcarriers in the frequency domain. Second receiving unit 1720 is configured to receive a second DMRS occupying a second frequency comb. The second frequency comb includes a second subset of the plurality of subcarriers in the frequency domain.

Example Embodiments Group A Embodiments

-   -   1. A method performed by a wireless device of transmitting an         uplink demodulation reference signal (DMRS), the method         comprising:         -   obtaining a first spreading function for spreading a first             pi/2-BPSK sequence to occupy a subset of carriers in the             frequency domain;         -   generating a first DMRS by applying the first spreading             function to the first pi/2-BPSK sequence, wherein the DMRS             is orthogonal to a second DMRS generated by another wireless             device using a second pi/2-BPSK sequence or a regular             DFTS-OFDM sequence and a second spreading function;         -   transmitting the first DMRS to a network node.     -   2. The method of embodiment 1, wherein the first spreading         function comprises a block spreading sequence.     -   3. The method of embodiment 1, wherein the first and second         pi/2-BPSK sequences coincide.     -   4. The method of any of embodiments 1-3, wherein each of the         pi/2-BPSK sequences comprise symbols from at least two alphabets         and fulfills one of:         -   the first and last elements of the pi/2-BPSK sequence are             from different alphabets; and         -   the first and last elements of the pi/2-BPSK sequence are             from a same alphabet and of a same sign.     -   5. The method of any of embodiments 1-4, wherein transmitting         the DMRS comprises applying bandwidth controlling processing,         such as PAPR controlling processing or pulse-shaping processing.     -   6. The method of any of embodiments 1-5, wherein the subset of         carriers in the frequency domain comprises a frequency-domain         comb.     -   7. A method performed by a wireless device for smoothing         waveform discontinuities, the method comprising:         -   transmitting a first DFTS-OFDM symbol;         -   setting the first one or more samples of a cyclic prefix to             zero or to a function of the last one or more samples of the             first DFTS-OFDM symbol; and         -   transmitting the cyclic prefix.     -   8. The method of any of the previous embodiments, further         comprising:         -   providing user data; and         -   forwarding the user data to a host computer via the             transmission to the base station.

Group B Embodiments

-   -   9. A method performed by a base station of receiving an uplink         demodulation reference signal (DMRS), the method comprising:         -   receiving a first DMRS generated using a first block             spreading sequence on a pi/2-BPSK sequence such that the             first DMRS occupies a first frequency comb; and         -   receiving a second DMRS orthogonal to the first DMRS and             occupying a second frequency comb.     -   10. The method of embodiment 9, wherein the second DMRS was         generated using a second block spreading sequence on a second         pi/2-BPSK sequence.     -   11. The method of embodiment 9, wherein the second DMRS was         generated using a regular DFTS-OFDM sequence.     -   12. The method of any of embodiments 8-10, wherein the first         DMRS was pulse shaped with a cyclic convolution maintaining the         comb structure.     -   13. The method of any of embodiments 8-11, wherein a last symbol         of the first DMRS sequence uses a different signaling alphabet         than a first symbol of the first DMRS sequence, or the last         symbol and the first symbol are from the same signaling alphabet         and have the same sign.     -   14. The method of any of the previous embodiments, further         comprising:         -   obtaining user data; and         -   forwarding the user data to a host computer or a wireless             device.

Group C Embodiments

-   -   15. A wireless device for transmitting an uplink demodulation         reference signal (DMRS), the wireless device comprising:         -   processing circuitry configured to perform any of the steps             of any of the Group A embodiments; and         -   power supply circuitry configured to supply power to the             wireless device.     -   16. A base station for receiving an uplink demodulation         reference signal (DMRS), the base station comprising:         -   processing circuitry configured to perform any of the steps             of any of the Group B embodiments;         -   power supply circuitry configured to supply power to the             wireless device.     -   17. A user equipment (UE) for transmitting an uplink         demodulation reference signal (DMRS), the UE comprising:         -   an antenna configured to send and receive wireless signals;         -   radio front-end circuitry connected to the antenna and to             processing circuitry, and configured to condition signals             communicated between the antenna and the processing             circuitry;         -   the processing circuitry being configured to perform any of             the steps of any of the Group A embodiments;         -   an input interface connected to the processing circuitry and             configured to allow input of information into the UE to be             processed by the processing circuitry;         -   an output interface connected to the processing circuitry             and configured to output information from the UE that has             been processed by the processing circuitry; and         -   a battery connected to the processing circuitry and             configured to supply power to the UE.     -   18. A communication system including a host computer comprising:         -   processing circuitry configured to provide user data; and         -   a communication interface configured to forward the user             data to a cellular network for transmission to a user             equipment (UE),         -   wherein the cellular network comprises a base station having             a radio interface and processing circuitry, the base             station's processing circuitry configured to perform any of             the steps of any of the Group B embodiments.     -   19. The communication system of the pervious embodiment further         including the base station.     -   20. The communication system of the previous 2 embodiments,         further including the UE, wherein the UE is configured to         communicate with the base station.     -   21. The communication system of the previous 3 embodiments,         wherein:         -   the processing circuitry of the host computer is configured             to execute a host application, thereby providing the user             data; and         -   the UE comprises processing circuitry configured to execute             a client application associated with the host application.     -   22. A method implemented in a communication system including a         host computer, a base station and a user equipment (UE), the         method comprising:         -   at the host computer, providing user data; and         -   at the host computer, initiating a transmission carrying the             user data to the UE via a cellular network comprising the             base station, wherein the base station performs any of the             steps of any of the Group B embodiments.     -   23. The method of the previous embodiment, further comprising,         at the base station, transmitting the user data.     -   24. The method of the previous 2 embodiments, wherein the user         data is provided at the host computer by executing a host         application, the method further comprising, at the UE, executing         a client application associated with the host application.     -   25. A user equipment (UE) configured to communicate with a base         station, the UE comprising a radio interface and processing         circuitry configured to perform the previous 3 embodiments.     -   26. A communication system including a host computer comprising:         -   processing circuitry configured to provide user data; and         -   a communication interface configured to forward user data to             a cellular network for transmission to a user equipment             (UE),         -   wherein the UE comprises a radio interface and processing             circuitry, the UE's components configured to perform any of             the steps of any of the Group A embodiments.     -   27. The communication system of the previous embodiment, wherein         the cellular network further includes a base station configured         to communicate with the UE.     -   28. The communication system of the previous 2 embodiments,         wherein:         -   the processing circuitry of the host computer is configured             to execute a host application, thereby providing the user             data; and         -   the UE's processing circuitry is configured to execute a             client application associated with the host application.     -   29. A method implemented in a communication system including a         host computer, a base station and a user equipment (UE), the         method comprising:         -   at the host computer, providing user data; and         -   at the host computer, initiating a transmission carrying the             user data to the UE via a cellular network comprising the             base station, wherein the UE performs any of the steps of             any of the Group A embodiments.     -   30. The method of the previous embodiment, further comprising at         the UE, receiving the user data from the base station.     -   31. A communication system including a host computer comprising:         -   communication interface configured to receive user data             originating from a transmission from a user equipment (UE)             to a base station,         -   wherein the UE comprises a radio interface and processing             circuitry, the UE's processing circuitry configured to             perform any of the steps of any of the Group A embodiments.     -   32. The communication system of the previous embodiment, further         including the UE.     -   33. The communication system of the previous 2 embodiments,         further including the base station, wherein the base station         comprises a radio interface configured to communicate with the         UE and a communication interface configured to forward to the         host computer the user data carried by a transmission from the         UE to the base station.     -   34. The communication system of the previous 3 embodiments,         wherein:         -   the processing circuitry of the host computer is configured             to execute a host application; and         -   the UE's processing circuitry is configured to execute a             client application associated with the host application,             thereby providing the user data.     -   35. The communication system of the previous 4 embodiments,         wherein:         -   the processing circuitry of the host computer is configured             to execute a host application, thereby providing request             data; and         -   the UE's processing circuitry is configured to execute a             client application associated with the host application,             thereby providing the user data in response to the request             data.     -   36. A method implemented in a communication system including a         host computer, a base station and a user equipment (UE), the         method comprising:         -   at the host computer, receiving user data transmitted to the             base station from the UE, wherein the UE performs any of the             steps of any of the Group A embodiments.     -   37. The method of the previous embodiment, further comprising,         at the UE, providing the user data to the base station.     -   38. The method of the previous 2 embodiments, further         comprising:         -   at the UE, executing a client application, thereby providing             the user data to be transmitted; and         -   at the host computer, executing a host application             associated with the client application.     -   39. The method of the previous 3 embodiments, further         comprising:         -   at the UE, executing a client application; and         -   at the UE, receiving input data to the client application,             the input data being provided at the host computer by             executing a host application associated with the client             application,         -   wherein the user data to be transmitted is provided by the             client application in response to the input data.     -   40. A communication system including a host computer comprising         a communication interface configured to receive user data         originating from a transmission from a user equipment (UE) to a         base station, wherein the base station comprises a radio         interface and processing circuitry, the base station's         processing circuitry configured to perform any of the steps of         any of the Group B embodiments.     -   41. The communication system of the previous embodiment further         including the base station.     -   42. The communication system of the previous 2 embodiments,         further including the UE, wherein the UE is configured to         communicate with the base station.     -   43. The communication system of the previous 3 embodiments,         wherein:         -   the processing circuitry of the host computer is configured             to execute a host application;         -   the UE is configured to execute a client application             associated with the host application, thereby providing the             user data to be received by the host computer.     -   44. A method implemented in a communication system including a         host computer, a base station and a user equipment (UE), the         method comprising:         -   at the host computer, receiving, from the base station, user             data originating from a transmission which the base station             has received from the UE, wherein the UE performs any of the             steps of any of the Group A embodiments.     -   45. The method of the previous embodiment, further comprising at         the base station, receiving the user data from the UE.     -   46. The method of the previous 2 embodiments, further comprising         at the base station, initiating a transmission of the received         user data to the host computer.

Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the disclosure. The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. Additionally, operations of the systems and apparatuses may be performed using any suitable logic comprising software, hardware, and/or other logic. As used in this document, “each” refers to each member of a set or each member of a subset of a set.

Modifications, additions, or omissions may be made to the methods described herein without departing from the scope of the disclosure. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order.

Although this disclosure has been described in terms of certain embodiments, alterations and permutations of the embodiments will be apparent to those skilled in the art. Accordingly, the above description of the embodiments does not constrain this disclosure. Other changes, substitutions, and alterations are possible without departing from the spirit and scope of this disclosure, as defined by the following claims.

Abbreviations

At least some of the following abbreviations may be used in this disclosure. If there is an inconsistency between abbreviations, preference should be given to how it is used above. If listed multiple times below, the first listing should be preferred over any subsequent listing(s).

-   -   BPSK Binary Phase Shift Keying     -   CM Cubic Metric     -   DFT Fast Fourier Transform     -   DM-RS Demodulation Reference Signal     -   FDSS Frequency-domain Pulse Shaper     -   MU-MIMO Multi-user MIMO     -   PAPR Peak to Average Power Ratio     -   PRB Physical Resource Block     -   UCI Uplink Control Information     -   1x RTT CDMA2000 1x Radio Transmission Technology     -   3GPP 3rd Generation Partnership Project     -   5G 5th Generation     -   ABS Almost Blank Subframe     -   ARQ Automatic Repeat Request     -   AWGN Additive White Gaussian Noise     -   BCCH Broadcast Control Channel     -   BCH Broadcast Channel     -   CA Carrier Aggregation     -   CC Carrier Component     -   CCCH SDU Common Control Channel SDU     -   CDMA Code Division Multiplexing Access     -   CGI Cell Global Identifier     -   CIR Channel Impulse Response     -   CP Cyclic Prefix     -   CPICH Common Pilot Channel     -   CPICH Ec/No CPICH Received energy per chip divided by the power         density in the band     -   CQI Channel Quality information     -   C-RNTI Cell RNTI     -   CSI Channel State Information     -   DCCH Dedicated Control Channel     -   DL Downlink     -   DM Demodulation     -   DMRS Demodulation Reference Signal     -   DRX Discontinuous Reception     -   DTX Discontinuous Transmission     -   DTCH Dedicated Traffic Channel     -   DUT Device Under Test     -   E-CID Enhanced Cell-ID (positioning method)     -   E-SMLC Evolved-Serving Mobile Location Centre     -   ECGI Evolved CGI     -   eNB E-UTRAN NodeB     -   ePDCCH enhanced Physical Downlink Control Channel     -   E-SMLC evolved Serving Mobile Location Center     -   E-UTRA Evolved UTRA     -   E-UTRAN Evolved UTRAN     -   FDD Frequency Division Duplex     -   FFS For Further Study     -   GERAN GSM EDGE Radio Access Network     -   gNB Base station in NR     -   GNSS Global Navigation Satellite System     -   GSM Global System for Mobile communication     -   HARQ Hybrid Automatic Repeat Request     -   HO Handover     -   HSPA High Speed Packet Access     -   HRPD High Rate Packet Data     -   LOS Line of Sight     -   LPP LTE Positioning Protocol     -   LTE Long-Term Evolution     -   MAC Medium Access Control     -   MBMS Multimedia Broadcast Multicast Services     -   MBSFN Multimedia Broadcast multicast service Single Frequency         Network     -   MBSFN ABS MBSFN Almost Blank Subframe     -   MDT Minimization of Drive Tests     -   MIB Master Information Block     -   MME Mobility Management Entity     -   MSC Mobile Switching Center     -   NPDCCH Narrowband Physical Downlink Control Channel     -   NR New Radio     -   OCNG OFDMA Channel Noise Generator     -   OFDM Orthogonal Frequency Division Multiplexing     -   OFDMA Orthogonal Frequency Division Multiple Access     -   OSS Operations Support System     -   OTDOA Observed Time Difference of Arrival     -   O&M Operation and Maintenance     -   PBCH Physical Broadcast Channel     -   P-CCPCH Primary Common Control Physical Channel     -   PCell Primary Cell     -   PCFICH Physical Control Format Indicator Channel     -   PDCCH Physical Downlink Control Channel     -   PDP Profile Delay Profile     -   PDSCH Physical Downlink Shared Channel     -   PGW Packet Gateway     -   PHICH Physical Hybrid-ARQ Indicator Channel     -   PLMN Public Land Mobile Network     -   PMI Precoder Matrix Indicator     -   PRACH Physical Random Access Channel     -   PRS Positioning Reference Signal     -   PSS Primary Synchronization Signal     -   PUCCH Physical Uplink Control Channel     -   PUSCH Physical Uplink Shared Channel     -   RACH Random Access Channel     -   QAM Quadrature Amplitude Modulation     -   RAN Radio Access Network     -   RAT Radio Access Technology     -   RLM Radio Link Management     -   RNC Radio Network Controller     -   RNTI Radio Network Temporary Identifier     -   RRC Radio Resource Control     -   RRM Radio Resource Management     -   RS Reference Signal     -   RSCP Received Signal Code Power     -   RSRP Reference Symbol Received Power OR Reference Signal         Received Power     -   RSRQ Reference Signal Received Quality OR Reference Symbol         Received Quality     -   RSSI Received Signal Strength Indicator     -   RSTD Reference Signal Time Difference     -   SCH Synchronization Channel     -   SCell Secondary Cell     -   SDU Service Data Unit     -   SFN System Frame Number     -   SGW Serving Gateway     -   SI System Information     -   SIB System Information Block     -   SNR Signal to Noise Ratio     -   SON Self Optimized Network     -   SS Synchronization Signal     -   SSS Secondary Synchronization Signal     -   TDD Time Division Duplex     -   TDOA Time Difference of Arrival     -   TOA Time of Arrival     -   TSS Tertiary Synchronization Signal     -   TTI Transmission Time Interval     -   UE User Equipment     -   UL Uplink     -   UMTS Universal Mobile Telecommunication System     -   USIM Universal Subscriber Identity Module     -   UTDOA Uplink Time Difference of Arrival     -   UTRA Universal Terrestrial Radio Access     -   UTRAN Universal Terrestrial Radio Access Network     -   WCDMA Wide CDMA     -   WLAN Wide Local Area Network 

1. A method performed by a wireless device for transmitting a demodulation reference signal (DMRS), the method comprising: obtaining a first spreading function for spreading a first pi/2-BPSK sequence to occupy a first subset of a plurality of subcarriers in a frequency domain; generating a first DMRS by applying the first spreading function to the first pi/2-BPSK sequence; and transmitting the first DMRS to a network node.
 2. The method of claim 1, further comprising performing Discrete Fourier Transform (DFT) precoding.
 3. The method of claim 1, wherein the first spreading function comprises a block spreading sequence.
 4. The method of claim 1, wherein the first DMRS is pulse shaped with a cyclic convolution maintaining the first subset of the plurality of subcarriers.
 5. The method of claim 1, wherein the first DMRS is orthogonal to a second DMRS, the second DMRS generated using a second spreading function for spreading a second pi/2-BPSK sequence or another DMRS sequence occupying a second subset of the plurality of subcarriers in the frequency domain.
 6. The method of claim 5, wherein the second DMRS is generated by the wireless device.
 7. The method of claim 5, wherein the second DMRS is generated by a wireless device other than the first wireless device.
 8. The method of claim 1 wherein the first pi/2-BPSK sequence is equal to the second pi/2-BPSK sequence.
 9. The method of claim 5, wherein: the first subset of the plurality of subcarriers over which the first DMRS is mapped on comprises a plurality of odd subcarriers within the plurality of subcarriers; and a second subset of a plurality of subcarriers over which the second DMRS is spread comprises a plurality of even subcarriers within the plurality of subcarriers.
 10. The method of claim 1, wherein the first pi/2-BPSK sequence comprises symbols from at least two alphabets and at least one of the following is true: a first element and a last element of the first pi/2-BPSK sequence are from different alphabets within the at least two alphabets; and the first element and the last element of the first pi/2-BPSK sequence are from a same alphabet and of a same sign.
 11. The method of claim 1, wherein the first DMRS comprises symbols from at least two alphabets and one of the following is true: a first element and a last element of the first DMRS are from different alphabets within the at least two alphabets, or the first element and the last element of the first DMRS are from a same alphabet and of a same sign.
 12. The method of claim 10, wherein the at least two alphabets comprise: a first alphabet that is {+1 −1}, and a second alphabet that is {+j −j}.
 13. The method of claim 1, wherein the first pi/2 BPSK sequence is of an even length.
 14. The method of claim 1, wherein transmitting the DMRS comprises applying bandwidth controlling processing, the bandwidth controlling processing comprising PAPR controlling processing or pulse-shaping processing or cyclic convolution.
 15. The method of claim 1, wherein the first subset of the plurality of subcarriers in the frequency domain comprises a frequency-domain comb that is less than an entire set of the plurality of subcarriers.
 16. The method of claim 1, the method further comprising performing Discrete Fourier Transform (DFT) precoding using a DFT precoder of size M, and wherein the first pi/2-BPSK sequence has a length of M/L, wherein L is a comb spacing in the frequency domain.
 17. The method of claim 1, further comprising: receiving, from a network node, information indicating that the wireless device is to use the first spreading function for spreading the first pi/2-BPSK sequence.
 18. A wireless device for transmitting a demodulation reference signal (DMRS), the wireless device comprising: memory storing instructions; and processing circuitry operable to execute the instructions to cause the wireless device to: obtain a first spreading function for spreading a first pi/2-BPSK sequence to occupy a first subset of a plurality of subcarriers in a frequency domain; generate a first DMRS by applying the first spreading function to the first pi/2-BPSK sequence; and transmit the first DMRS to a network node. 19.-34. (canceled)
 35. A method performed by a network node for receiving a demodulation reference signal (DMRS), the method comprising: receiving a first DMRS generated using a first spreading function applied to a first pi/2-BPSK sequence such that the first DMRS occupies a first frequency comb, the frequency comb comprising a first subset of a plurality of subcarriers in the frequency domain; and receiving a second DMRS occupying a second frequency comb, the second frequency comb comprising a second subset of the plurality of subcarriers in the frequency domain. 36.-45. (canceled)
 46. A network node for configuring a wireless device to transmit a demodulation reference signal (DMRS), the network node comprising: memory storing instructions; and processing circuitry operable to execute the instructions to cause the network node to: receive a first DMRS generated using a first spreading function applied to a first pi/2-BPSK sequence such that the first DMRS occupies a first frequency comb, the frequency comb comprising a first subset of a plurality of carriers in the frequency domain; and receive a second DMRS occupying a second frequency comb, the second frequency comb comprising a second subset of the plurality of carriers in the frequency domain. 47.-56. (canceled) 